Coil filament

ABSTRACT

A coiled filament has a light emitter with a reduced volume as best possible to serve in downsizing a light bulb and elevate an illumination with high efficiency in an illuminated field. A flat coiled filament ( 1 ) wound into flatness is arranged in the form of a helix or ring, locating the longer axis (FL) of the flatness in parallel with the central axis (CL) of the coiled filament or to cross the central axis (CL) at an appropriate angle (α) including right angle. Alternatively, it is arranged in coincident with the radial axis (HL) of the coiled filament or at an appropriate angle (α) including the radial axis (HL). Alternatively, the flat coiled filament is U-shaped and a pair of such U-shaped flat coiled filaments ( 4 ) are mated with each other through their open ends, while the inner surfaces of their closed ends are kept non-contact with each other. Alternatively, the flat coiled filament ( 1 ) is formed circular, and within a circle of such a circular ring-shaped double coiled filament ( 5, 10, 12 ), an appropriate number of straight or circular flat coiled filaments ( 6, 7, 9, 11, 13, 14 ) are arranged in the central axis (CL) of the circle.

FIELD OF THE INVENTION

The present invention relates to a coiled filament having a lightemitter with a reduced volume as best possible to serve in downsizing alight bulb and elevate an illumination with high efficiency in anilluminated field.

BACKGROUND OF THE INVENTION

Generally, for increasing the amount of filament per unit volume todownsize a light bulb and elevate an illumination in an illuminatedfield, methods of arranging multiple coiled filaments closely, and ofwinding coils double, triple or quadruple have been known, for example.These methods have limitations, however, in increasing the amount offilament per unit volume. Recently, plane form of the coiled filamentitself is designed in different forms, such as elliptic and polygonal,rather than circular to increase the amount of filament per unit volume.For example, plane form of the coiled filament may be changed fromcircular into flat. Alternatively, as disclosed by the Inventor(s) inCoiled filament for Light Bulbs (see Japanese Patent ApplicationLaid-Open No. 2000-82444), a cylindrical coil in plane form, or circularseen from a plane, of the coiled filament can be altered. In this case,the coil rim is bent toward the center of the circle to reduce the planearea. These methods are capable of increasing the amount of filament perunit volume, downsizing a light bulb closer to a spotlight compared tothe conventional coiled filament, and improving the radiationefficiency.

As descried above, if plane form of the coiled filament may be shapedflat in plane form, or the rim of the circle in plane form of the coiledfilament may be bent toward the center of the circle, it is possible toincrease the amount of filament per unit volume compared to theconventional cylindrical coiled filament. This is effective to downsizea light bulb and improve the radiation efficiency to some extent.However, it is desired to develop such a coiled filament that serves infurther downsizing the light bulb with higher radiation efficiency.

The present invention is intended to solve the above problems in the artand accordingly has an object to provide a coiled filament having alight emitter with a reduced volume as best possible, which can serve indownsizing a light bulb and elevate an illumination with high efficiencyin an illuminated field.

SUMMARY OF THE INVENTION

To solve the above problems, a coiled filament according to a firstaspect of the invention comprises a straight flat coiled filament woundinto flatness in the form of a straight line, wherein the longer axis ofthe flatness is located in parallel with the central axis of a doublecoiled filament formed by further winding the straight flat coiledfilament, and the straight flat coiled filament is arranged helicallyabout the central axis. In this case, instead of arranging the straightflat coiled filament helically about the central axis of the doublecoiled filament, the straight flat coiled filament may be ring-shapedabout the central axis, and a plurality of such ring-shaped flat coiledfilaments may be arranged in parallel with the axial direction of thecentral axis. When a double coiled filament is formed, it is not limitedto a circular double coiled filament but may be formed in a flat doublecoiled filament.

Thus, on production of the coiled filament, the flat coiled filament maybe helically wound to produce the double coiled filament, or the flatcoiled filament may be ring-shaped to produce the double coiled filamentwith multiple such ring-shaped filaments arranged in parallel. Comparedto the conventional double coiled filament formed helical or ring-shapedusing the cylindrically wound filament, the flat coiled filament woundin flat cylindrical form of the present invention is advantageous toform a double coiled filament with a smaller winding diameter of thedouble coil reduced by the extent of the flatness. Accordingly, it ispossible to increase the amount of filament per unit volume, downsizethe light bulb smaller and elevate the illumination in the illuminatedfield higher than the conventional types are. Further, on production ofthe double coiled filament, if preferably it is formed in a flatcylindrical double coiled filament, a plurality of such flat cylindricaldouble coiled filaments can be arranged to further increase the amountof filament per unit volume.

A coiled filament according to a second aspect of the present inventioncomprises a straight flat coiled filament wound into flatness in theform of a straight line, wherein the longer axis of the flatnessfilament is located at an appropriate angle including right angle tocross the central axis of a double coiled filament formed by furtherwinding the straight flat coil, and the straight flat coiled filament isarranged helically about the central axis. Also in this case, instead ofarranging the straight flat coiled filament helically about the centralaxis of the double coiled filament, the straight flat coiled filamentmay be ring-shaped about the central axis, and a plurality of suchring-shaped flat coiled filaments may be arranged in parallel with theaxial direction of the central axis. When a double coiled filament isformed, it is not limited to a circular double coiled filament but maybe formed in a flat double coiled filament.

Thus, on production of the coiled filament, the flat coiled filament inthe form of a straight line wound into flatness is arranged, locatingthe longer axis of the flatness at an appropriate angle including rightangle to cross the central axis of a double coiled filament formed byfurther winding a straight flat coiled filament. As a result, comparedto the first aspect of the invention, it is possible to further narrow agap between each flat coiled filament and increase the amount offilament per unit volume.

A coiled filament according to a third aspect of the invention comprisesa plurality of flat coiled filaments wound into flatness in the form ofstraight lines, wherein the straight lines are located in parallel witha pre-determined central axis, and the longer axes of the flatness ofthe straight flat coiled filaments are located at an appropriate angleto cross the radial directions of the pre-determined central axisincluding the radial direction. In this case, the straight flat coiledfilaments may be located by an appropriate number, matching the longeraxes of the flatness thereof with the axes in the radial directions of apre-determined central axis, or they may be located by an appropriatenumber, setting the longer axes to cross the axes in the radialdirections at an appropriate angle. Alternatively, as a combination ofthem, a plurality of straight flat coiled filaments may be arranged inparallel longitudinally and laterally about the central axis seen from aplane.

Thus, the plural flat coiled filaments in the form of straight lines arearranged, locating the straight lines in parallel with a pre-determinedcentral axis, and locating the longer axes of the flatness of thestraight flat coiled filaments at an appropriate angle to cross theradial directions of the pre-determined central axis including theradial direction. As a result, one end in the longitudinal direction ofeach of the plural flat coiled filaments can be approached to thecentral axis as close as an approach limit. Therefore, it is possible toextremely increase the amount of filament per unit volume when the flatcoiled filaments are arranged as many as an arrangement limit.

A coiled filament according to a forth aspect of the invention comprisesa flat coiled filament wound into flatness in the form of a straightline and further U-shaped, wherein a pair of such U-shaped flat coiledfilaments are inserted into each other through their open ends, andinner surfaces of their closed ends are kept non-contact with eachother. In this case, the U-shaped flat coiled filaments are not limitedto a pair but a plurality of pairs may be inserted mutually throughtheir open ends.

Thus, the flat coiled filament is U-shape, and a pair of such U-shapedflat coiled filaments are mated with each other through their open ends,while the inner surfaces of their closed ends are kept non-contact witheach other. As a result, it is possible to increase the amount offilament per unit volume and easily produce the coiled filament becausethe arrangement is simple.

A coiled filament according to a fifth aspect of the invention comprisesa flat coiled filament wound into flatness in the form of a straightline and further formed circular, wherein an appropriate number of flatcoiled filaments are arranged within a circle of such a circularring-shaped double coiled filament in the central axis direction of thecircle. In this case, the flat coiled filament arranged in the centralaxis direction of the circular ring-shaped double coiled filament maycomprise a straight flat coiled filament, or a circular ring-shapeddouble coiled filament with a smaller diameter than that of the circularring-shaped double coiled filament. Alternatively, a plurality of theflat coiled filaments arranged in the central axis direction of thecircular ring-shaped double coiled filament may sandwich the circularring-shaped double coiled filament to be located before and behind thecentral axis thereof. Alternatively, these aspects may be combinedappropriately.

Thus, the flat coiled filament in the form of a straight line is formedcircular, and within a circle of such a circular ring-shaped doublecoiled filament, an appropriate number of flat coiled filaments arearranged in the central axis direction of the circle. Therefore, it ispossible to increase the amount of filament per unit volume. Inaddition, as the illuminated field can be formed circular rather thanrectangular, it is possible to reduce the light emission loss at thelight emitter on the corner of the rectangle as far as possible toachieve a high efficiency of light emission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of the coiled filament according to thepresent invention: (a) a front view of a double coiled filament formedby helically winding a flat coiled filament; (b) a plan view of thedouble coiled filament formed cylindrical; (c) a plan view of the doublecoiled filament formed flat cylindrical; and (d) a partly enlarge viewof the double coiled filament.

FIG. 2 shows a second embodiment of the coiled filament according to thepresent invention: (a) a front view of a double coiled filament formedby helically winding a flat coiled filament, locating the longer axis ofthe flatness to cross the central axis of the double coiled filament atan appropriate angle; (b) a plan view of the double coiled filamentformed cylindrical; (c) a plan view of the double coiled filament formedflat cylindrical; and (d) a partly enlarge view of the double coiledfilament.

FIG. 3 shows an alternative of the embodiment of FIG. 2: (a) a frontview of a double coiled filament formed by helically winding a flatcoiled filament, locating the longer axis of the flatness to cross thecentral axis of the double coiled filament at right angle; (b) a planview of the double coiled filament formed cylindrical; and (c) a planview of the double coiled filament formed flat cylindrical.

FIG. 4 shows a third embodiment of the coiled filament according to thepresent invention: (a) a front view of a ring-shaped double coiledfilament formed by winding a plurality of ring-shaped straight flatcoiled filaments in parallel with the axial direction of the centralaxis, locating the longer axis of the flatness in parallel with thecentral axis of the double coiled filament; (b) a plan view of thering-shaped double coiled filament formed cylindrical; and (c) a planview of the ring-shaped double coiled filament formed flat cylindrical.

FIG. 5 shows a fourth embodiment of the coiled filament according to thepresent invention: (a) a front view of a ring-shaped double coiledfilament formed by winding a plurality of ring-shaped flat coiledfilaments and arranged in parallel with the axial direction of thecentral axis, locating the longer axis of the flatness to cross thecentral axis of the double coiled filament at an appropriate angle; (b)a plan view of the ring-shaped double coiled filament formedcylindrical; and (c) a plan view of the ring-shaped double coiledfilament formed flat cylindrical.

FIG. 6 shows an alternative of the embodiment of FIG. 5: (a) a frontview of a ring-shaped double coiled filament formed by winding aplurality of ring-shaped straight flat coiled filaments and arranged inparallel with the axial direction of the central axis, locating thelonger axis of the flatness to cross the central axis of the doublecoiled filament at right angle; (b) a plan view of the ring-shapeddouble coiled filament formed cylindrical; and (c) a plan view of thering-shaped double coiled filament formed flat cylindrical.

FIG. 7 shows a fifth embodiment of the coiled filament according to thepresent invention: (a) a front view of a plurality of flat coiledfilaments in the form of straight lines arranged in such a state thatthe straight lines are located in parallel with a pre-determined centralaxis, and the longer axes of the flatness of the straight flat coiledfilaments are located in coincident with the radial directions of thecentral axis; and (b) a plan view thereof.

FIG. 8 shows an alternative of the embodiment of FIG. 7 in a plan viewof a coiled filament formed by winding a plurality of flat coiledfilaments in the form of straight lines in such a state that thestraight lines are located in parallel with and at an equal angle to apre-determined central axis, and the longer axes of the flatness of thestraight flat coiled filaments are located to cross the radialdirections of the central axis at an appropriate angle.

FIG. 9 shows another alternative of the embodiment of FIG. 7 in a planview of a coiled filament formed by winding a plurality of flat coiledfilaments in the form of straight lines in such a state that thestraight lines are located in parallel with a pre-determined centralaxis, and the longer axes of the flatness of the straight flat coiledfilaments are located in coincident with the radial directions of thecentral axis, and to cross the radial directions of the central axis atan appropriate angle, in combination.

FIG. 10 shows a sixth embodiment of the coiled filament according to thepresent invention: (a) a front view of a pair of straight flat coiledfilaments each U-shaped and inserted into each other through their openends, crossing the longer axes of the flatness in the U-shaped flatcoiled filaments at right angle; (b) a plan view thereof; and (c) abottom view of (a).

FIG. 11 shows an alternative of the embodiment of FIG. 10: (a) a frontview of a pair of U-shaped flat coiled filaments in such a state thatthe longer axes FL of the flatness in the U-shaped flat coiled filamentsare located in parallel; (b) a plan view thereof; and (c) a bottom viewof (a).

FIG. 12 shows a seventh embodiment of the coiled filament according tothe present invention: (a) a front view of a straight flat coiledfilament formed circular in such a state that the circular ring-shapeddouble coiled filament contains flat coiled filaments within its circle;and (b) a plan view of (a) partly cut-off.

FIG. 13 shows an alternative of the embodiment of FIG. 12: (a) a frontview in such a state that the straight flat coiled filament at thecenter in FIG. 12(a) is turned to a different direction and located infront of the circular ring-shaped double coiled filament; and (b) a planview of (a) partly cut-off.

FIG. 14 shows another alternative of the embodiment of FIG. 12: (a) afront view in such a state that the straight flat coiled filament at thecenter in FIG. 13(a) is removed, and the circular ring-shaped doublecoiled filament and the straight flat coiled filaments located withinthe circle are turned to a different direction; and (b) a bottom viewthereof.

FIG. 15 shows an eighth embodiment of the coiled filament according tothe present invention: (a) a front view in such a state that the longeraxis of the flatness of a straight flat coiled filament is located incoincident with the radial direction of the central axis of the circleof a circular ring-shaped double coiled filament, and within the circle,a similarly-formed smaller-diameter circular ring-shaped double coiledfilament is located coaxially; and (b) a cross-sectional view takenacross the center thereof.

FIG. 16 shows an alternative of the embodiment of FIG. 15: (a) a frontview in such a state that the longer axis of the flatness of thecircular ring-shaped double coiled filament is located in parallel withthe central axis of the circle of the circular ring-shaped double coiledfilament, and within the circle, a pair of similarly-formeddifferent-diameter circular ring-shaped double coiled filaments arelocated coaxially; and (b) a bottom view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the coiled filament according to the present inventionwill be described below based on the drawings.

First Embodiment (FIG. 1)

The figure shows (a) a front view of a double coiled filament formed byhelically winding a flat coiled filament; (b) a plan view of the doublecoiled filament formed cylindrical; (c) a plan view of the double coiledfilament formed flat cylindrical; and (d) a partly enlarge view of thedouble coiled filament.

A straight flat coiled filament 1 wound into flatness and formed in anelongated straight line is employed to form a cylindrical or flatcylindrical double coiled filament 2, 3 having a central axis CL, asshown in FIG. 1(a)-(d). Locating its longitudinal axis FL in parallelwith the central axis CL, the straight flat coiled filament 1 is woundhelically to produce an objective coiled filament A, A1.

In this case, spacing S1, S1 a, between the central axis CL of thedouble coiled filament 2, 3 and the inner rim of the cylindrical doublecoiled filament 2 formed in a cylindrical double coil or the inner rimat the shorter side of the flat cylindrical double coiled filament 3formed in a flat, cylindrical double coiled filament, and spacing S2,between each coil of the helically-wound double coiled filament 2, 3,are designed as narrow as possible outside a range that causesarc-related troubles to increase the amount of filament per unit volume.When the straight flat coiled filament 1 is employed to form thecylindrical or flat cylindrical double coiled filament 2, 3, forexample, it is formed into the flat cylindrical double coiled filament 3as shown in FIG. 1(c), the spacing S1 a between the inner rim at theshorter side and the central axis CL can be designed much shorter thanthe spacing S1 in the cylindrical double coiled filament 2. Therefore,if cylindrical double coiled filaments having plural central axes arelocated arranging the shorter sides in line, it is possible to increasethe amount of filament per unit volume by the extent accordingly.

For convenience of description in the following embodiments, thestraight flat coiled filament 1 is shown as wounded into a single coil,though it is free to form it into a double coil (ditto in each followingembodiment).

Second Embodiment (FIGS. 2 and 3)

FIG. 2 shows (a) a front view of a double coiled filament formed byhelically winding a flat coiled filament, locating the longer axis ofthe flatness to cross the central axis of the double coiled filament atan appropriate angle; (b) a plan view of the double coiled filamentformed cylindrical; (c) a plan view of the double coiled filament formedflat cylindrical; and (d) a partly enlarge view of the double coiledfilament.

As shown in FIG. 2(a)-(d), a straight flat coiled filament 1 similarlyformed as in the first embodiment is employed to form a cylindrical orflat cylindrical double coiled filament 4, 5. In this case, locating thelonger axis FL of the flatness to cross the central axis CL of thedouble coiled filament 4, 5 at an appropriate angle a, the straight flatcoiled filament 1 is wound helically to produce an objective coiledfilament B, B1.

Also in this case, similar to the first embodiment, spacing S3, S3 a,between the central axis CL of the double coiled filament 4, 5 and theinner rim of the cylindrical double coiled filament 4 formed in acylindrical double coil or the inner rim at the shorter side of the flatcylindrical double coiled filament 5 formed in a flat, cylindricaldouble coiled filament, and spacing S4, between each coil of thehelically-wound double coiled filament 4, 5, are designed as narrow aspossible outside a range that causes arc-related troubles to increasethe amount of filament per unit volume.

When the straight flat coiled filament is employed to form thecylindrical or flat cylindrical double coiled filament 4, 5, forexample, it is formed into the flat cylindrical double coiled filament 5as shown in FIG. 2(c), the spacing S3 a between the inner rim at theshorter side and the central axis CL can be designed much shorter thanthat in the cylindrical double coiled filament 4. Therefore, if aplurality of cylindrical double coiled filaments having plural centralaxes are located, arranging the shorter sides in line, it is possible toincrease the amount of filament per unit volume by the extentaccordingly. This is also similar to the first embodiment.

FIG. 3 shows (a) a front view of a double coiled filament formed byhelically winding a flat coiled filament, locating the longer axis ofthe flatness to cross the central axis of the double coiled filament atright angle; (b) a plan view of the double coiled filament formedcylindrical; and (c) a plan view of the double coiled filament formedflat cylindrical.

As shown in FIG. 3, locating the longer axis FL to cross the centralaxis CL of the double coiled filament 4, 5 at right angle (α=90°), thestraight flat coiled filament 1 is wound helically to produce anobjective coiled filament C, C1.

Also in this case, similar to the first embodiment, spacing S5, S5 a,between the central axis CL of the double coiled filament and the innerrim of the cylindrical double coiled filament 6 formed in a cylindricaldouble coil or the inner rim at the shorter side of the flat cylindricaldouble coiled filament 7 formed in a flat, cylindrical double coiledfilament, and spacing S6, between each coil of the helically-wounddouble coiled filament 6, 7, are designed as narrow as possible outsidea range that causes arc-related troubles to increase the amount offilament per unit volume.

On formation of a double coiled filament, for example, a flatcylindrical double coiled filament as shown in FIG. 3(c), the spacing S5a between the inner rim at the shorter side and the central axis CL canbe designed much shorter than that in the cylindrical double coiledfilament 6. Therefore, if cylindrical double coiled filaments havingplural central axes are located, arranging the shorter sides in line, itis possible to increase the amount of filament per unit volume by theextent accordingly. This is also similar to the first embodiment.

Third Embodiment (FIG. 4)

FIG. 4 shows (a) a front view of a ring-shaped double coiled filamentformed by winding a plurality of ring-shaped straight flat coiledfilaments in parallel with the axial direction of the central axis,locating the longer axis of the flatness and arranged in parallel withthe central axis of the double coiled filament; (b) a plan view of thering-shaped double coiled filament formed cylindrical; and (c) a planview of the ring-shaped double coiled filament formed flat cylindrical.

The straight flat coiled filament 1 is ring-shaped to produce aring-shaped double coiled filament 8, 9. In the ring-shaped doublecoiled filament 8, 9, the longer axis FL of the flatness in the straightflat coiled filament 1 is located in parallel with the central axis CLof the ring-shaped double coiled filament. In addition, an appropriatenumber of the ring-shaped double coiled filaments 8, 9 are arranged inparallel with the axial direction of the central axis CL of thering-shaped double coiled filament to produce an objective coiledfilament D, D1.

Also in this case, spacing S7, S7 a, between the central axis CL of thering-shaped double coiled filament 8, 9 and the inner rim of thecircular ring-shaped double coiled filament 8 formed in a circular andring-shaped double coil or the inner rim at the shorter side of the flatring-shaped double coiled filament 9 formed in a flat and ring-shapeddouble coiled filament, and spacing S8, between each ring of thering-shaped double coiled filament 8, 9, are designed as narrow aspossible outside a range that causes arc-related troubles to increasethe amount of filament per unit volume.

On formation of a ring-shaped double coiled filament, for example, aflat ring-shaped double coiled filament formed flat in plane as shown inFIG. 4(c), the spacing S7 a between the inner rim at the shorter sideand the central axis CL can be designed much shorter than the spacing S7in the ring-shaped double coiled filament 8 formed circular in plane.Therefore,if double coiled filaments having plural central axes arelocated, arranging the shorter sides in line, it is possible to increasethe amount of filament per unit volume by the extent accordingly. Thisis also similar to the first embodiment.

Fourth Embodiment (FIG. 5 and FIG. 6)

FIG. 5 shows (a) a front view of a ring-shaped double coiled filamentformed by winding a plurality of ring-shaped flat coiled filaments andarranged in parallel with the axial direction of the central axis,locating the longer axis of the flatness to cross the central axis ofthe double coiled filament at an appropriate angle; (b) a plan view ofthe ring-shaped double coiled filament formed cylindrical; and (c) aplan view of the ring-shaped double coiled filament formed flatcylindrical.

As shown in FIG. 5, the straight flat coiled filament 1 is ring-shapedto produce a ring-shaped double coiled filament 10, 11. In thering-shaped double coiled filament 10, 11, the longer axis FL of theflatness in the straight flat coiled filament 1 is located to cross thecentral axis CL of the ring-shaped double coiled filament 10, 11 at anappropriate angle c. In addition, an appropriate number of thering-shaped double coiled filaments 10, 11 are arranged in parallel withthe axial direction of the central axis CL thereof to produce anobjective coiled filament D, D1.

Also in this case, spacing S9, S9 a, between the central axis CL of thering-shaped double coiled filament 10, 11 and the inner rim of thecircular ring-shaped double coiled filament 10 formed in a circular andring-shaped double coil or the inner rim at the shorter side of the flatring-shaped double coiled filament 11 formed in a flat and ring-shapeddouble coiled filament, and spacing S10, between each ring of thering-shaped double coiled filament 10, 11, are designed as narrow aspossible outside a range that causes arc-related troubles to increasethe amount of filament per unit volume.

On formation of a ring-shaped double coiled filament, for example, aring-shaped flat double coiled filament 11 formed flat in plane as shownin FIG. 5(c), the spacing S9 a between the inner rim at the shorter sideand the central axis CL can be designed much shorter than the spacing S9in the ring-shaped double coiled filament 10 formed circular in plane.Therefore, if double coiled filaments having plural central axes arelocated, arranging the shorter sides in line, it is possible to increasethe amount of filament per unit volume by the extent accordingly. Thisis also similar to the first embodiment.

FIG. 6 shows (a) a front view of a ring-shaped double coiled filamentformed by winding a plurality of ring-shaped straight flat coiledfilaments and arranged in parallel with the axial direction of thecentral axis, locating the longer axis of the flatness to cross thecentral axis of the double coiled filament at right angle; (b) a planview of the ring-shaped double coiled filament formed cylindrical; and(c) a plan view of the ring-shaped double coiled filament formed flatcylindrical.

As shown in FIG. 6, in ring-shaped double coiled filament 12, 13 formedsimilarly as FIG. 5, the longer axis FL of the flatness in the straightflat coiled filament 1 is located to cross the central axis CL of thering-shaped double coiled filament 12, 13 at right angle (α=90°). Inaddition, an appropriate number of the ring-shaped double coiledfilaments 12, 13 are arranged in parallel with the axial direction ofthe central axis CL thereof to produce an objective coiled filament E,E1.

Also in this case, spacing S11, S11 a, between the central axis CL ofthe ring-shaped double coiled filament 12, 13 and the inner rim of thecircular ring-shaped double coiled filament 12 formed in a circular andring-shaped double coil or the inner rim at the shorter side of the flatring-shaped double coiled filament 13 formed in a flat and ring-shapeddouble coiled filament, and spacing S12, between each ring of thering-shaped double coiled filament 12, 13, are designed as narrow aspossible outside a range that causes arc-related troubles to increasethe amount of filament per unit volume.

On formation of a ring-shaped double coiled filament, for example, if aflat ring-shaped double coiled filament 13 is formed flat in plane asshown in FIG. 6(c), the spacing S11 a between the inner rim at theshorter side and the central axis CL can be designed much shorter thanthe spacing S11 in the ring-shaped double coiled filament 12 formedcircular in plane. Therefore, if a plurality of ring-shaped doublecoiled filaments are located, arranging the shorter sides in line, it ispossible to increase the amount of filament per unit volume by theextent accordingly.

Fifth Embodiment (FIGS. 7-9)

FIG. 7 shows (a) a front view of a plurality of flat coiled filaments inthe form of straight lines arranged in such a state that the straightlines are located in parallel with a pre-determined central axis, andthe longer axes of the flatness of the straight flat coiled filamentsare located in coincident with the radial directions of the centralaxis; and (b) a plan view thereof.

As shown in FIG. 7, four straight flat coiled filaments 14, formedsimilarly as the first embodiment and appropriately elongated, arearranged in such a state that straight lines SL, which is the axes ofthe coils of the straight flat coiled filaments, are located in parallelwith a pre-determined central axis CL and at every 90-degree about thecentral axis CL. In addition, the longer axes FL of the flatness of thestraight flat coiled filaments 14 are located in coincident with theradial directions HL of the above-mentioned pre-determined central axisCL in the same plane to produce an objective coiled filament F.

FIG. 8 is a plan view of a coiled filament formed by winding a pluralityof flat coiled filaments in the form of straight lines in such a statethat the straight lines are located in parallel with and at an equalangle to a pre-determined central axis, and the longer axes of theflatness of the straight flat coiled filaments are located to cross theradial directions of the central axis at an appropriate angle.

As shown in FIG. 8, six straight flat coiled filaments 14, formedsimilarly as FIG. 7 and appropriately elongated, are arranged in such astate that their straight lines (not depicted) are located in parallelwith and at equal angle about a pre-determined central axis CL. Inaddition, the longer axes FL of the flatness of the straight flat coiledfilaments 14 are located to cross the radial directions HL of thepre-determined central axis CL at an appropriate angle α in the sameplane to produce an objective coiled filament F1.

FIG. 9 is a plan view of a coiled filament formed by winding a pluralityof flat coiled filaments in the form of straight lines in such a statethat the straight lines are located in parallel with a pre-determinedcentral axis, and the longer axes of the flatness of the straight flatcoiled filaments are located in coincident with the radial directions ofthe central axis, and to cross the radial directions of the central axisat an appropriate angle, in combination.

As shown in FIG. 9, six straight flat coiled filaments 14, formedsimilarly as FIG. 7 and appropriately elongated, are arranged in such astate that their straight lines (not depicted) are located in parallelwith a pre-determined central axis CL. In addition, the longer axes FLof the flatness of the straight flat coiled filaments 14 are partlylocated in coincident with the radial directions HL of thepre-determined central axis CL in the same plane. At the same time, thelonger axes FL are partly located to cross the radial directions HL ofthe pre-determined central axis CL at an appropriate angle α in the sameplane. In such a combination, the six straight flat coiled filaments arearranged in parallel longitudinally and laterally about the central axisCL seen from a plane to produce an objective coiled filament F2.

In either case of FIGS. 7-9, about the pre-determined central axis CL ofthe coiled filament F, F1, F2, spacing S1, S13, S15, S16 between thecentral axis CL and one end 14 a of each flat coiled filament 14 at thecentral axis CL in the longitudinal direction, and spacing S12, S14,S17, S18 between each flat coiled filament 14 are designed as narrow aspossible outside a range that causes arc-related troubles to increasethe amount of filament per unit volume.

Sixth Emboidment (FIGS. 10 and 11)

FIG. 10 shows (a) a front view of a pair of straight flat coiledfilaments each U-shaped and inserted into each other through their openends, crossing the longer axes of the flatness in the U-shaped flatcoiled filaments at right angle; (b) a plan view thereof; and (c) abottom view of (a).

As shown in FIG. 10, the straight flat coiled filament, formed similarlyas the first embodiment, is further U-shaped. The longer axes FL of theflatness at both open ends of the U-shaped coiled filament 15 arelocated on the same axis. A pair of the U-shaped coiled filaments 15 arecrossed with each other at right angle and mutually inserted through theopen ends while keeping the inner surfaces of the closed endsnon-contact with each other to produce an objective coiled filament G.

FIG. 11 shows (a) a front view of a pair of U-shaped flat coiledfilaments in such a state that the longer axes FL of the flatness in theU-shaped flat coiled filaments are located in parallel; (b) a plan viewthereof; and (c) a bottom view of (a).

As shown in FIG. 11, when the pair of the U-shaped coiled filaments 15of FIG. 10 are mutually inserted through the open ends, the longer axesFL of the flat coiled filaments are arranged in parallel to produce anobjective coiled filament G1.

In the cases of FIGS. 10-11, either of the pair of the U-shaped coiledfilaments 15 may be plural, or one may be plural and the other single.The spacing S19 between the inner surfaces of the U-shaped coiledfilament 15 in the coiled filament G, G1 and the spacing S20 between theU-shaped coiled filaments 15 are designed as narrow as possible outsidea range that causes arc-related troubles to increase the amount offilament per unit volume.

Seventh Embodiment (FIGS. 12-14)

FIG. 12 shows (a) a front view of a straight flat coiled filament formedcircular in such a state that the circular ring-shaped double coiledfilament contains flat coiled filaments within its circle; and (b) aplan view of (a) partly cut-off.

As shown in FIG. 12, the straight flat coiled filament, formed similarlyas the first embodiment, is further formed circular to produce acircular ring-shaped double coiled filament 16.

With in the circle of the circular ring-shaped double coiled filament16, at the rear along the central axis CL of the circle, three straightflat coiled filaments 17, 18 are arranged at an equal interval. As forthe circular ring-shaped double coiled filament 16, the longer axis FLof the flatness is located in parallel with the central axis CL of thecircle. As for the three straight flat coiled filaments 17, 18 that arearranged at the rear along the central axis CL of the circle, the longeraxes FL of the flatness are located in parallel with the central axis CLof the circle. Among the straight flat coiled filaments 17, 18, thestraight flat coiled filament 17 at the center has a length slightlyshorter than the inner diameter of the circle. The straight coiledfilaments 18 located at both sides have shorter lengths than a lengththat contacts the extension of the inner rim of the circle to produce anobjective coiled filament H.

FIG. 13 shows (a) a front view in such a state that the straight flatcoiled filament at the center in FIG. 12(a) is turned to a differentdirection and located in front of the circular ring-shaped double coiledfilament; and (b) a plan view of (a) partly cut-off.

As shown in FIG. 13, among the three straight flat coiled filaments 17,18 in FIG. 12, as for the straight flat coiled filament 17 at thecenter, the longer axis FL of the flatness is located to cross thecenter axis CL of the circular ring-shaped double coiled filament 16. Inaddition, it is located at the front of the circular ring-shaped doublecoiled filament 16 as a straight flat coiled filament 17 a to produce anobjective coiled filament H1.

FIG. 14 shows (a) a front view in such a state that the straight flatcoiled filament at the center in FIG. 13(a) is removed, and the circularring-shaped double coiled filament and the straight flat coiledfilaments located within the circle are turned to a different direction;and (b) a bottom view thereof.

As shown in FIG. 14, among the three straight flat coiled filaments 17,18 in FIG. 12, the straight flat coiled filament 17 at the center isremoved. Matching the longer axis FL of the flatness of the straightflat coiled filament with the radial direction HL of the central axis CLof the circular ring-shaped double coiled filament 16 in the same plane,the circular ring-shaped double coiled filament 16 is formed into acircular ring-shaped double coiled filament 19. Within the circle of thecircular ring-shaped double coiled filament 19, a pair of straight flatcoiled filaments 20 are arranged at an appropriate interval. Inaddition, the longer axis FL of the flatness of the straight flat coiledfilament 20 is located behind the circular ring-shaped double coiledfilament 19 to cross the central axis CL at right angle to produce anobjective coiled filament H2.

In either case of FIGS. 12-14, spacing S21-S24 between the circularring-shaped double coiled filament 16, 19 and the straight flat coiledfilament 17, 18, 20, and spacing S28-S30 between the straight flatcoiled filaments 17, 18, 20 are designed as narrow as possible outside arange that causes arc-related troubles to increase the amount offilament per unit volume.

In addition, as for the circular ring-shaped double coiled filament 16,19 and the straight flat coiled filament 17, 18, 20 arranged within thecircle thereof, their lengths and sizes can be formed appropriatelywithin an effective range that does not interfere with each other at theillumination in the illuminated field to produce an objective coiledfilament H, H1, H2.

Eighth Embodiment (FIGS. 15 and 16)

FIG. 15 shows (a) a front view in such a state that the longer axis ofthe flatness of a straight flat coiled filament is located in coincidentwith the radial direction of the central axis of the circle of acircular ring-shaped double coiled filament, and within the circle, asimilarly-formed smaller-diameter circular ring-shaped double coiledfilament is located coaxially; and (b) a cross-sectional view takenacross the center thereof.

As shown in FIG. 15, the straight flat coiled filament, formed similarlyas the first embodiment, is employed to produce a circular ring-shapeddouble coiled filament 21, matching the longer axis FL of the flatcoiled filament with the radial direction HL of the central axis CL ofthe circular ring-shaped double coiled filament 21 in the same plane.Within the circle of the circular ring-shaped double coiled filament 21,behind along and coaxially about the central axis CL of the circle, acircular ring-shaped double coiled filament 22 with a smaller diametercompared to the circular ring-shaped double coiled filament 21 isarranged to produce an objective coiled filament J.

FIG. 16 shows (a) a front view in such a state that the longer axis ofthe flatness of the circular ring-shaped double coiled filament islocated in parallel with the central axis of the circle of the circularring-shaped double coiled filament, and within the circle, a pair ofsimilarly-formed different-diameter circular ring-shaped double coiledfilaments are located coaxially; and (b) a bottom view thereof.

As shown in FIG. 16, the circular ring-shaped double coiled filament ofFIG. 15 is modified such that the longer axis FL of the flatness islocated in parallel with the central axis CL of the circle of thecircular ring-shaped double coiled filament, to produce a circularring-shaped double coiled filament 23. Within the circle of the circularring-shaped double coiled filament 23, before and behind the circularring-shaped double coiled filament 23 along the central axis CL, a pairof circular ring-shaped double coiled filaments 24, 25 with differentdiameters are arranged to produce an objective coiled filament J1.

In either case of FIGS. 15 and 16, spacing S25-S27 between the circularring-shaped double coiled filaments 21 and 22, and 23, 24 and 25 aredesigned as narrow as possible outside a range that causes arc-relatedtroubles to increase the amount of filament per unit volume.

In addition, as for the basic circular ring-shaped double coiledfilaments 21, 23 and the smaller-diameter circular ring-shaped doublecoiled filament 22, 24, 25 arranged within the circle thereof, theirlengths and sizes can be formed appropriately within an effective rangethat does not interfere with each other at the illumination in theilluminated field to produce an objective coiled filament.

As described above, according to the coiled filament of the presentinvention, it is possible to increase the amount of filament per unitvolume compared to the conventional coiled filament. Therefore, it ispossible to reduce the volume of the light emitter in a coiled filament.This is effective to serve in downsizing a light bulb and improve theillumination per unit area with high efficiency in an illuminated fieldwithout variations.

1. A coiled filament comprising a straight flat coiled filament wound into flatness in the form of a straight line, wherein the longer axis of said flatness is located in parallel with the central axis of a double coiled filament formed by further winding said straight flat coiled filament, and said straight flat coiled filament is arranged helically about said central axis.
 2. A coiled filament comprising a straight flat coiled filament wound into flatness in the form of a straight line, wherein the longer axis of said flatness is located at an appropriate angle including right angle to cross the central axis of a double coiled filament formed by further winding said straight flat coiled filament, and said straight flat coiled filament is arranged helically about said central axis.
 3. The coiled filament according to any one of claims land 2, wherein said straight flat coiled filament is ring-shaped about the central axis of said double coiled filament, and a plurality of such ring-shaped flat coiled filaments are arranged in parallel with the axial direction of said central axis.
 4. A coiled filament comprising a plurality of flat coiled filaments wound into flatness in the form of straight lines, wherein said straight lines are located in parallel with a pre-determined central axis, and the longer axes of said flatness of said straight flat coiled filaments are located at an appropriate angle to cross the radial directions of said pre-determined central axis including said radial direction.
 5. A coiled filament comprising a flat coiled filament wound into flatness in the form of a straight line and further U-shaped, wherein a pair of such U-shaped flat coiled filaments are inserted into each other through their open ends, and inner surfaces of their closed ends are kept non-contact with each other.
 6. A coiled filament comprising a flat coiled filament wound into flatness in the form of a straight line and further formed circular, wherein an appropriate number of flat coiled filaments are arranged within a circle of such a circular ring-shaped double coiled filament in the central axis direction of said circle.
 7. The coiled filament according to claim 6, wherein said flat coiled filament arranged in the central axis direction of said circular ring-shaped double coiled filament comprises a straight flat coiled filament.
 8. The coiled filament according to claim 6, wherein said flat coiled filament arranged in the central axis direction of said circular ring-shaped double coiled filament comprises a circular ring-shaped double coiled filament with a smaller diameter than that of said circular ring-shaped double coiled filament.
 9. The coiled filament according to any one of claims 6-8, wherein a plurality of said flat coiled filaments arranged in the central axis direction of said circular ring-shaped double coiled filament sandwich said circular ring-shaped double coiled filament to be located before and behind the central axis thereof. 